Key Technical Points for Field Management of Rice During the Green-Returning and Tillering Stage
The green-returning and tillering stage of rice refers to the period from transplanting to the time before jointing and booting. This period is important for determining the number of panicles and laying the foundation for panicle and grain development. The main goal of field management is to promote good root development, rapid green-returning, and early tillering, to form sufficiently strong tillers and prevent stiff seedlings.
The main measures for field management are:
1. Scientific irrigation
To meet the physiological water requirements of rice, water should be used to regulate the growth and development of the rice plants and achieve the growth appearance required for high yield. Water management during the green-returning and tillering stage should achieve “one-cun water for green-returning”, “shallow water to promote tillering”, and “drain the field when enough tillers have formed”.
1) “One-cun water for green-returning”. Because the roots of rice seedlings are damaged during transplanting, their water-absorbing capacity is weak, while leaf transpiration does not decrease, so they easily lose water balance. If the seedlings are submerged too deeply, they are also prone to oxygen deficiency, death, or delayed green-returning. Therefore, maintaining a water layer of about 1 cun in the field can create a relatively heat-retaining and moisture-retaining warm and humid environment, ease the contradiction between water loss and water supply, and promote the occurrence of new roots and rapid green-returning and establishment.
2) “Shallow water to promote tillering”. During the tillering stage, the paddy field should be irrigated frequently with shallow water and kept under a thin water layer. Its effects are: first, it can meet the needs of leaf transpiration of the rice plants, allow metabolism to proceed normally, and promote the growth of tillers and leaves; second, it can allow the base of the rice plants and the soil to receive sunlight, raise soil temperature and water temperature, increase soil oxygen content and available nutrients, and benefit root growth and tiller formation; third, it is conducive to the sprouting of low-position tiller buds, lowering the tillering node position, shortening the leaf sheath, allowing tillers to emerge rapidly, advancing heading, and increasing the rate of productive tillers.
3) “Drain the field when enough tillers have formed”. Through investigation of the tillering dynamics in the field, when the total number of stems and tillers in the whole field reaches the number of seedlings needed for the target panicle number, drain the field in time. The main effects of draining the field are: first, renewing the soil environment, enhancing root vigor, and strengthening microbial activity; second, controlling ineffective tillers, consolidating effective tillers, and increasing the rate of productive tillers; third, helping strengthen the stems and enhancing lodging resistance; fourth, regulating growth appearance, improving plant constitution, and reducing diseases and insect pests.
2. Scientific topdressing of tillering fertilizer
The tillering stage of rice is the period of most vigorous nitrogen metabolism in the whole life of rice. If fertilizer is insufficient, leaf emergence of the rice plants is slow, tillering is reduced, and root growth is poor. Therefore, tillering fertilizer should be topdressed scientifically. Topdressing tillering fertilizer should be based on a comprehensive analysis and full consideration of the soil fertility status of the paddy field, the application rate of basal fertilizer (middle-layer fertilizer), and the growth appearance of the rice plants in the field, and then decide whether to apply it, what fertilizer to apply, and how much to apply. Tillering fertilizer is generally topdressed 7-10 days after transplanting. For fields with high soil fertility and sufficient basal fertilizer (middle-layer fertilizer) application, tillering fertilizer may be applied less or not at all. Otherwise, tillering fertilizer should be applied early and in greater amount. The usual amount of tillering fertilizer is 5-7 kg of urea per mu. In the middle and late tillering stage, if the seedlings are found to grow poorly, the plants turn yellow, and there are signs of fertilizer deficiency, a small amount of adjustment fertilizer or tiller-preserving fertilizer may be applied, generally 3-5 kg of urea per mu. For fields with cold-waterlogged autumn stagnation and susceptibility to akagare disease, in addition to topdressing quick-acting nitrogen fertilizer, phosphorus and potassium fertilizers should also be added, and at the same time 0.2% zinc sulfate solution should be sprayed 2-3 times in time, once every 7-10 days, to prevent stiff seedlings. In short, through scientific topdressing of tillering fertilizer, it is necessary to ensure that about 35 days after transplanting, the maximum stem and tiller number reaches 80-90% of the preset target (350,000-400,000).
3. Intertillage and weed control
For intertillage and weed control in rice, manual pulling was used in the past, and later chemical weed control was adopted. Now, in order to control farmland non-point source pollution and protect Erhai Lake, Dali City has proposed “cancel chemical weed control and advocate manual pulling”. In view of the fact that the conditions for comprehensively “canceling chemical weed control” across large areas of rice have not yet been fully met, it is suggested that for intertillage and weed control in rice, safe, efficient, low-toxicity, and low-residue new herbicides may be selected for chemical weed control, generally 10-15 days after transplanting. Per mu, 100-150 ml of 60% butachlor plus 15 g of 10% nongdeshi (bensulfuron-methyl) wettable powder may be applied by the poisoned soil method, and after application the water layer should be maintained at 3-5 cm for one week. The weed control effect is relatively good, killing a broad spectrum of weeds and having a long efficacy.
4. Timely control of diseases, insect pests, and rodent damage
The main diseases during the green-returning and tillering stage of rice include leaf blast and stripe virus disease. The main insect pests include armyworm and stem borer. The main rodent damage is from field mice. Control should be carried out in time according to forecasting and field investigation. Leaf blast can be controlled with sulfur azole, stripe virus disease should be controlled in conjunction with unified control of rice planthoppers, and at the same time junkeduke can be used for control, armyworm can be controlled with kung fu, stem borer can be controlled with shachongshuang, and rodent damage can be controlled by placing diphacinone sodium salt “poison bait”.